1. Technical Field
The present subject matter relates to a method for calibrating a trigger unit which is connected via a trigger line to at least two sensors that can be triggered, each sensor being connected between two successive line portions of the trigger line, wherein each sensor has an input for one line portion of the trigger line and an output for the other line portion of the trigger line, a controllable interrupter between the input and output, and a control circuit connected to the input and controlling the interrupter, wherein the interrupters of all sensors are initially open. The present subject matter also relates to a sensor for such a method.
2. Background Art
A number of spatially distributed sensors are frequently used in measuring systems, for example in order to record object scenes multi-dimensionally. If a number of sensors on a trigger line are to be triggered, that is to say activated, simultaneously by a common trigger signal, the propagation time of the trigger signal over the trigger line thus changes the actual trigger point of each sensor and is to be taken into consideration with time-critical measurements, for example with propagation time measurements. Besides the line length, the propagation time over the trigger line is also dependent on temperature fluctuations and signs of aging, and therefore a highly accurate measurement of the propagation time of the trigger signal, if this only occurs once, leads to just limited accuracy however.
Spatially distributed transmitters and receivers of a radar system which are coupled to one another in order to carry out a multi-dimensional sampling procedure are known from EP 1 570 291 B1 under the term “multistatic sensor systems”. The radar transmitters and receivers are coupled in this case with the aid of a signal generator for each of the transmitters and receivers with adaptable clock signals of frequencies which deviate slightly from one another and which are transmitted via a common signal line. The signal line is formed in bus topology with branches to each sensor. Here, the sequence of the largely structurally identical sensors on the trigger or signal line must be known for correct assignment of the measured data; it is generally programmed manually for this purpose following the establishment of the system or a sensor replacement, which is complex and additionally susceptible to faults.
The document DE 097 40 306 A1 describes a method for initialization of a bus system with an additional initialization line on which bus modules are connected in a cascade. To initialize a bus master, at first each bus module disconnects the initialization line to the bus module following in the cascade; the bus master then enquires about a device identifier of the last accessible bus module in the cascade, which, after the inquiry, unblocks the initialization line to the module following in the cascade and thereby the bus master progressively determines the sequence of the bus modules on the trigger line.